diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c index 4834a809985a..175c08a6e41e 100644 --- a/kernel/liveupdate/kexec_handover.c +++ b/kernel/liveupdate/kexec_handover.c @@ -38,6 +38,16 @@ #include "../kexec_internal.h" #include "kexec_handover_internal.h" +/* + * This is the minimal alignment required by deferred struct page init. + * deferred_init_memmap_chunk frees memory to the buddy allocator, which looks + * at the neighboring pages (up to MAX_PAGE_ORDER) to merge them. + * If KHO scratch is not aligned to that value, buddy can access uninitialized + * struct pages, which can cause a crash. + */ +#define SCRATCH_ALIGNMENT_BYTES (PAGE_SIZE * MAX_ORDER_NR_PAGES) +static_assert(SCRATCH_ALIGNMENT_BYTES >= CMA_MIN_ALIGNMENT_BYTES); + /* The magic token for preserved pages */ #define KHO_PAGE_MAGIC 0x4b484f50U /* ASCII for 'KHOP' */ @@ -640,8 +650,8 @@ static void __init scratch_size_update(void) * Scratch areas are released as MIGRATE_CMA. Round them up to the right * size. */ - scratch_size_lowmem = round_up(scratch_size_lowmem, CMA_MIN_ALIGNMENT_BYTES); - scratch_size_global = round_up(scratch_size_global, CMA_MIN_ALIGNMENT_BYTES); + scratch_size_lowmem = round_up(scratch_size_lowmem, SCRATCH_ALIGNMENT_BYTES); + scratch_size_global = round_up(scratch_size_global, SCRATCH_ALIGNMENT_BYTES); } static phys_addr_t __init scratch_size_node(int nid) @@ -656,7 +666,7 @@ static phys_addr_t __init scratch_size_node(int nid) size = scratch_size_pernode; } - return round_up(size, CMA_MIN_ALIGNMENT_BYTES); + return round_up(size, SCRATCH_ALIGNMENT_BYTES); } /** @@ -692,7 +702,7 @@ static void __init kho_reserve_scratch(void) * next kernel */ size = scratch_size_lowmem; - addr = memblock_phys_alloc_range(size, CMA_MIN_ALIGNMENT_BYTES, 0, + addr = memblock_phys_alloc_range(size, SCRATCH_ALIGNMENT_BYTES, 0, ARCH_LOW_ADDRESS_LIMIT); if (!addr) { pr_err("Failed to reserve lowmem scratch buffer\n"); @@ -705,7 +715,7 @@ static void __init kho_reserve_scratch(void) /* reserve large contiguous area for allocations without nid */ size = scratch_size_global; - addr = memblock_phys_alloc(size, CMA_MIN_ALIGNMENT_BYTES); + addr = memblock_phys_alloc(size, SCRATCH_ALIGNMENT_BYTES); if (!addr) { pr_err("Failed to reserve global scratch buffer\n"); goto err_free_scratch_areas; @@ -721,7 +731,7 @@ static void __init kho_reserve_scratch(void) */ for_each_node_state(nid, N_MEMORY) { size = scratch_size_node(nid); - addr = memblock_alloc_range_nid(size, CMA_MIN_ALIGNMENT_BYTES, + addr = memblock_alloc_range_nid(size, SCRATCH_ALIGNMENT_BYTES, 0, MEMBLOCK_ALLOC_ACCESSIBLE, nid, true); if (!addr) {